Open-Cell Reticulated Foam

ABSTRACT

A foam for use in a lost-foam casting process utilized in the manufacture of a component for a gas turbine engine, the foam having a void fraction less than or equal to ninety five percent, is disclosed. The foam may include a first layer comprising polymer foam having an open-cell structure and a void fraction greater than ninety five percent. A second layer, comprising adhesive, may be adhered to the first layer. A third layer comprising particulate material may be adhered to the second layer.

FIELD OF THE DISCLOSURE

This disclosure generally relates to open-cell reticulated foam and,more specifically, to open-cell reticulated foam for use in the creationof gas turbine engine fan blades.

BACKGROUND OF THE DISCLOSURE

In order to increase operational efficiency, and thereby decrease fuelconsumption, designers of gas turbine engines continually pursue ways todecrease component weight while maintaining resilience necessary for theoperation of such engine. Fan blades are no exception.

One way gas turbine engine designers have utilized to reduce fan bladeweight is by employing an open-cell reticulated metal foam coreenveloped by an outer shell of a resilient second material that formsthe airfoil. In one design, the outer shell is manufactured from a metalor metal alloy. In another design, the outer shell is comprised of oneor more layers of composite material.

Such fan blade designs are not without complication. The void fractionof the open-cell reticulated foam utilized to manufacture such metalfoam is commonly about ninety seven percent. While not necessarilyconclusive, data suggests that the ligaments and nodes of metal foamscreated with the use of such high void fraction open-cell reticulatedfoams lack the strength and mechanical properties necessary for use in afan blade. Accordingly, a need exists for modified, open-cellreticulated foams that can be used as a precursor to manufactureopen-cell cell reticulated metal foams for a gas turbine engine fanblade. This disclosure is directed toward this end.

SUMMARY OF THE DISCLOSURE

In accordance with one embodiment of the present disclosure, a foam foruse in a lost-foam casting process, the foam having a void fraction lessthan or equal to ninety five percent, is disclosed. The foam maycomprise a first layer made of polymer foam having an open-cellstructure and a void fraction greater than ninety five percent. The foammay further include a second layer of an adhesive adhered to the firstlayer. Finally, the foam may include a third layer comprising aparticulate material adhered to the second layer.

In a refinement of the foam for use in a lost foam casting process, thefoam having a void fraction less than or equal to ninety five percent,the polymer foam may be selected from the group consisting ofpolyurethane polymer foam, polyvinyl chloride polymer foam, polystyrenepolymer foam, polyimide polymer foam, silicone polymer foam,polyethylene polymer foam, polyester polymer foam and combinationsthereof.

In another refinement of the foam for use in a lost foam castingprocess, the foam having a void fraction less than or equal to ninetyfive percent, the adhesive may be an adhesive polymer selected from thegroup consisting of acrylic polymer, alkyd polymer, styrene acrylicpolymer, styrene butadiene polymer, vinyl acetate polymer, vinyl acetatehomopolymer polymer, vinyl acrylic polymer, vinyl maleate polymer, vinylversatate polymer, vinyl alcohol polymer, polyvinyl chloride polymer,polyvinylpyrrolidone polymer, casein and combinations thereof.

In another refinement of the foam for use in a lost foam castingprocess, the foam having a void fraction less than or equal to ninetyfive percent, the particulate material may be selected from the groupconsisting of wax powder, wood flour, polymer powder and combinationsthereof.

In another refinement of the foam for use in a lost foam castingprocess, the foam having a void fraction less than or equal to ninetyfive percent, the wax powder may be selected from the group consistingof animal wax powder, vegetable wax powder, mineral wax powder,petroleum wax powder and combinations thereof.

In another refinement of the foam for use in a lost foam castingprocess, the foam having a void fraction less than or equal to ninetyfive percent, the polymer powder may be selected from the groupconsisting of polyurethane polymer powder, polyvinyl chloride polymerpowder, polystyrene polymer powder, polyimide polymer powder,polyethylene polymer powder, polyester polymer powder, polypropylenepolymer powder and combinations thereof.

In accordance with another embodiment of the present disclosure, amethod for manufacturing foam for use in a lost-foam casting process,the foam having a void fraction less than or equal to ninety fivepercent, is disclosed. The method may include providing polymer foamhaving an open-cell structure and a void fraction greater than ninetyfive percent. Then, the polymer foam may be coated with an adhesive.Finally, particulate matter may be applied to the adhesive.

In a refinement of the method for manufacturing the foam for use in alost-foam casting process, the foam having a void fraction less thanninety five percent, the polymer foam may be selected from the groupconsisting of polyurethane polymer foam, polyvinyl chloride polymerfoam, polystyrene polymer foam, polyimide polymer foam, silicone polymerfoam, polyethylene polymer foam, polyester polymer foam and combinationsthereof.

In another refinement of the method for manufacturing the foam for usein a lost-foam casting process, the foam having a void fraction lessthan ninety five percent, the adhesive may comprise an adhesive polymer,and the adhesive polymer may be selected from the group consisting ofacrylic polymer, alkyd polymer, styrene acrylic polymer, styrenebutadiene polymer, vinyl acetate polymer, vinyl acetate homopolymerpolymer, vinyl acrylic polymer, vinyl maleate polymer, vinyl versatatepolymer, vinyl alcohol polymer, polyvinyl chloride polymer,polyvinylpyrrolidone polymer, casein and combinations thereof.

In another refinement of the method for manufacturing the foam for usein a lost-foam casting process, the foam having a void fraction lessthan ninety five percent, the particulate material may be selected fromthe group consisting of wax powder, wood flour, polymer powder andcombinations thereof.

In another refinement of the method for manufacturing the foam for usein a lost-foam casting process, the foam having a void fraction lessthan ninety five percent, the wax powder may be selected from the groupconsisting of animal wax powder, vegetable wax powder, mineral waxpowder, petroleum wax powder and combinations thereof.

In another refinement of the method for manufacturing the foam for usein a lost-foam casting process, the foam having a void fraction lessthan ninety five percent, the polymer powder may be selected from thegroup consisting of polyurethane polymer powder, polyvinyl chloridepolymer powder, polystyrene polymer powder, polyimide polymer powder,polyethylene polymer powder, polyester polymer powder, polypropylenepolymer powder and combinations thereof.

In another refinement of the method for manufacturing the foam for usein a lost-foam casting process, the foam having a void fraction lessthan ninety five percent, the coating the polymer foam with an adhesivestep may comprise applying an emulsion to the polymer foam, and theemulsion may comprise an adhesive polymer and solvent.

In another refinement of the method for manufacturing the foam for usein a lost-foam casting process, the foam having a void fraction lessthan ninety five percent, the method may further include the process ofremoving excess solvent from the polymer foam before applying aparticulate material to the adhesive.

In another refinement of the method for manufacturing the foam for usein a lost-foam casting process, the foam having a void fraction lessthan ninety five percent, the method may further include wherein thepolymer foam comprises ligaments positioned between nodes, and furthercomprising heating the foam to a temperature above the meltingtemperature of the particulate material, followed by cooling the foam toa temperature below the melting temperature of the particulate materialto form a substantially continuous coating of particulate material overthe ligaments.

In another refinement of the method for manufacturing the foam for usein a lost-foam casting process, the foam having a void fraction lessthan ninety five percent, the applying a particulate material to theadhesive may include passing the adhesive coated polymer foam through afluidized bed of particulate material.

In accordance with another embodiment of the present disclosure, amethod for manufacturing a fan blade for a gas turbine engine isdisclosed. The method may include, providing polymer foam having anopen-cell structure and a void fraction greater than ninety fivepercent, followed by coating the polymer foam with an adhesive to createadhesive coated foam. In a next step, a particulate material may beapplied to the adhesive coated foam to make a modified foam having avoid fraction less than or equal to ninety five percent. Then, themodified foam having a void fraction less than or equal to ninety fivepercent may be covered with a refractory material, and then thisrefractory material may be cured until it hardens to form an investment.Next, the investment casting may be heated to a temperature above theboiling point of the modified foam having avoid fraction less than orequal to ninety five percent to form a negative of modified foam. Then,molten metal or metal alloy may be added to the negative, and thenegative may be cooled to a temperature below the melting temperature ofthe metal or metal alloy to form a positive of the modified foam. In anext step, the refractory material may be removed to form an open-cellmetal foam having a void fraction less than or equal to ninety fivepercent. Finally, the open cell metal foam having a void fraction lessthan or equal to ninety five percent may be enveloped with an outershell of first material, the outer shell having the shape of an airfoil,to form a fan blade for a gas turbine engine.

In a refinement of the method for manufacturing the fan blade for a gasturbine engine, the polymer foam may be polyurethane polymer foam, theadhesive may be vinyl acetate, the particulate material may bepolyethylene polymer powder and the metal or metal alloy may bealuminum.

In another refinement of the method for manufacturing the fan blade fora gas turbine engine, the outer shell of a first material may be made ofa metal or metal alloy selected from the group consisting of aluminum,titanium and nickel, aluminum alloys, steel, nickel alloys and titaniumalloys.

In another refinement of the method for manufacturing the fan blade fora gas turbine engine, the outer shell of a first material may be made ofa composite material, and the composite material may be made fiberembedded in resin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side, partially cross-sectional view of a gas turbine engineconstructed in accordance with the present disclosure.

FIG. 2 is a perspective view of an exemplary gas turbine engine fanblade assembly that may be used in conjunction with the gas turbineengine of FIG. 1.

FIG. 3 is a perspective view of an exemplary fan blade that may be usedin conjunction with the fan blade assembly of FIG. 2.

FIG. 4 is a cross-sectional view of the exemplary fan blade that may beused in conjunction with the fan blade assembly of FIG. 2 taken alongline 3-3 of FIG. 3.

FIG. 5 is a schematic illustration depicting open-cell polymer foam foruse in the manufacture of open-cell reticulated metal foam, theopen-celled reticulated metal foam able to be used in the manufacture ofthe exemplary fan blade depicted in FIGS. 3-4.

FIGS. 6(a-b) are schematic illustrations depicting two modified,open-cell polymer foams for use in the manufacture of open-cellreticulated metal foam, the open-cell reticulated metal foam able to beused in the manufacture of the exemplary fan blade depicted in FIGS.3-4.

FIG. 7 is a flowchart depicting an exemplary method for preparing amodified, open-cell reticulated foam for use in the manufacture of anopen-cell reticulated metal foam, the open-cell reticulated metal foamable to be used in the manufacture of the exemplary fan blade depictedin FIGS. 3-4.

FIG. 8 is a flowchart depicting an exemplary method for preparing theexemplary fan blade depicted in FIGS. 3-4 utilizing the open-cellpolymer foams of FIGS. 5-6 in a lost-foam casting process.

These and other aspects and features of the present disclosure will bemore readily understood when read in conjunction with the accompanyingdrawings.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring now to the drawings, and with specific reference to FIG. 1, agas turbine engine is shown and generally referred to be referencenumeral 20. The gas turbine engine 20 disclosed herein as a two-spoolturbofan that generally incorporates a fan section 22, a compressorsection 24, a combustor section 26 and a turbine section 28. Alternativeengines might include an augmentor section (not shown) among othersystems or features. The fan section 22 drives air along a bypassflowpath B, while the compressor section 24 drives air along a coreflowpath C for compression and communication into the combustor section26. As will be described in further detail herein, in the combustionsection 26, the compressor air is mixed with fuel and ignited, with theresulting combustion gases then expanding in turbine section 28.Although depicted as a turbofan gas turbine engine in the disclosednon-limiting embodiment, it should be understood that the conceptsdescribed herein are not limited to use with turbofans as the teachingsmay be applied to other types of turbine engines including, but notlimited to, three-spool architectures as well.

The engine 20 generally includes a low speed spool 30 and a high speedspool 32 mounted for rotation about an engine central longitudinal axisA relative to an engine static structure 36 via several bearing systems38. It should be understood that various bearing systems 38 at variouslocations may alternatively or additionally be provided.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan blade assembly 42, a low pressure (or first)compressor section 44 and a low pressure (or first) turbine section 46.The inner shaft 40 is connected to the fan blade assembly 42 through ageared architecture 48 to drive the fan assembly 42 at a lower speedthan the low speed spool 30. The high speed spool 32 includes an outershaft 50 that interconnects a high pressure (or second) compressorsection 52 and high pressure (or second) turbine section 54. The outershaft 50 is typically concentric with and radially outward from theinner shaft 50. A combustor 56 is arranged between the high pressurecompressor 52 and the high pressure turbine 54. A mid-turbine frame 57of the engine static structure 36 is arranged generally between the highpressure turbine 54 and the low pressure turbine 46. The mid-turbineframe 57 supports one or more bearing systems 38 in the turbine section28. The inner shaft 40 and the outer shaft 50 are concentric and rotatevia bearing systems 38 about the engine central longitudinal axis A,which is collinear with their longitudinal axes. As used herein, a “highpressure” compressor or turbine experiences a higher pressure than acorresponding “low pressure” compressor or turbine.

The core airflow C is compressed first by the low pressure compressor44, and then by the high pressure compressor 52, before being mixed andburned with fuel in the combustor 56, and lastly expanded over the highpressure turbine 54 and low pressure turbine 46. The mid-turbine frame57 includes airfoils 59 which are in the core airflow path. The turbines46, 54 rotationally drive the respective low speed spool 30 and highspeed spool 32 in response to the expansion.

The engine 20 in one example is a high-bypass geared aircraft engine. Ina high-bypass engine a greater volume of air moves along a bypassflowpath B than through core airflow C. The ratio of the mass of airmoving through bypass flowpath B to core airflow C is known as thebypass ratio. In a further example, the engine 20 bypass ratio isgreater than about six (6), with an example embodiment being greaterthan ten (10), the geared architecture 48 is an epicyclic gear train,such as a star gear system or other gear system, with a gear reductionratio of greater than about 2.3 and the low pressure turbine 46 has apressure ratio that is greater than about 5. In one disclosedembodiment, the engine 20 bypass ratio is greater than about ten (10:1),the fan diameter is significantly larger than that of the low pressurecompressor 44, and the low pressure turbine 46 has a pressure ratio thatis greater than about 5:1. Low pressure turbine 46 pressure ratio ispressure measured prior to inlet of low pressure turbine 46 as relatedto the pressure at the outlet of the low pressure turbine 46 prior to anexhaust nozzle. It should be understood, however, that the aboveparameters are only exemplary of one embodiment of a geared architectureengine and that the present invention is applicable to other gas turbineengines including direct drive turbofans.

Referring to FIGS. 2 and 3, a fan blade 60 of the fan blade assembly 42may include a root 62 supporting a platform 64. An airfoil 66 may extendfrom the platform 64 to a tip 68. The airfoil 66 includes spaced apartleading and trailing edges 70, 72. Pressure and suction sides 74, 76adjoin the leading and trailing edges 70, 72 to provide a fan bladecontour 78. In certain embodiments the fan blade includes a leading edgesheath 80. The sheath 80 is secured to the fan blade 60 over the edge82. In one example, the sheath 80 is constructed from titanium. Inanother example, the sheath 80 is made from titanium alloy. It should beunderstood that other metals or materials may be used for sheath 80.

Now with reference to FIGS. 3-4, in one aspect of the presentdisclosure, the fan blade 60 may include a core 84 of open-cellreticulated metal foam enveloped by an outer shell 86 of a firstmaterial. Although other configurations are possible, in one embodimentthe core 84 may extend from the about the tip 68 to about the root 62.Similarly, the core 84 may extend from about the leading edge 70 toabout the trailing edge 72. Furthermore, in an additional embodiment,the fan blade may include a second core (not shown) being made of thefirst material surrounded by the shell 86.

The open-cell reticulated metal foam of the core 84 may be made of ametal or a metal alloy. Although other metals are certainly possible,some metals from which the open-cell reticulated metal foam core 84 maybe made consists of aluminum, titanium, nickel, copper, lead,molybdenum, tin, zinc and combinations thereof. Some metal alloys fromwhich open-cell metal foam of the core 84 may be made includes aluminumalloy, nickel alloy, titanium alloy, steel and combinations thereof.Examples of metal alloys from which the core 84 may be selected includesaluminum alloys, steel, nickel alloys and titanium alloys, such asseries 2000, 6000 or 7000 aluminum, 300 and 400 series stainless steels,precipitation hardenable stainless steels, Ti-6Al-4V,Ti-6Al-2Sn-4Zr-2Mo, WASPALOY®, INCONEL 718®, INCONEL 718+®, INCONEL 939®or HAYNES 282®. Other metal alloys are certainly possible.

In one design, the first material comprising the outer shell 86 may be ametal or a metal alloy. While the following list is not meant to beexhaustive, the metal from which outer shell 86 may be made includes,but is not limited to, aluminum, titanium and nickel. Some examples ofmetal alloys from which the outer shell 86 may be selected includesaluminum alloys, steel, nickel alloys and titanium alloys, such asseries 2000, 6000 or 7000 aluminum, 300 and 400 series stainless steels,precipitation hardenable stainless steels, Ti-6Al-4V,Ti-6Al-2Sn-4Zr-2Mo, WASPALOY®, INCONEL 718®, INCONEL 718+®, INCONEL 939®or HAYNES 282®.

In another design, the first material comprising the outer shell 86 maybe a composite material. Such composite material may be made of fiberembedded in resin. Some examples of the fibers from which the compositematerial may be made include, carbon-fiber,poly(p-phenylene-2,6-benzobisoxazole) fiber, mullite fiber, aluminafiber, silicon nitride fiber, silicon carbide fiber, boron fiber, boronnitride fiber, boron carbide fiber, glass fiber, titanium diboridefiber, yttria stabilized zirconium fiber and combinations thereof. Otherfibers are certainly possible.

The resin of such composite material may be a thermoset resin or athermoplastic resin. Examples of resins from which the compositematerial may be made includes, but is not limited to, polyester,thermoset urethane, cyanate ester, vinyl ester, polyimide, bisphenol Aepoxy, bisphenol F epoxy, novolac epoxy, glycidyl epoxy, cycloaliphaticepoxy, glycidylamine epoxy, melamine, phenol formaldehyde,polyhexahydrotriazine, low density polyethylene, medium densitypolyethylene, high density polyethylene, ultra-high molecular weightpolyethylene, polyvinyl chloride, polyethylene terephthalate, vinyl,polypropylene, poly(methyl methacrylate), nylon, polybenzimidazole,polystyrene, polytetrafluroethylene, polyetherimide, polyether ketone,polyether ether ketone, acrylonitrile butadiene styrene, styreneacrylonitrile, acrylonitrile styrene acrylate, polyamide, polyaryl etherketone, polycarbonate, polyoxymethylene, polyphenylene ether,polyphenylene sulfide, polysulfone, polybutylene terephthalate andcombinations thereof.

Now with reference to FIGS. 5-6(a-b), foam for use in a lost-foamcasting process, such as during the creation of open-cell reticulatedmetal foam for gas turbine engine fan blades 60, for example, isgenerally referred to by the reference number 88. Generally speaking,such foam 88 may have a reticulated three-dimensional structurecomprising one or more ligaments 90 extending between two or more nodes92. Being a three-dimensional structure, a ligament 90 may extendbetween two or more nodes 92 out of the same plane.

Now turning specifically to FIG. 5, such foam 88 may comprise a firstlayer 94 made of polymer foam having a void fraction greater than orequal to ninety five (95) percent. While other polymer foams arecertainly possible, some polymer foams from which the first layer 94 maybe made includes polyurethane polymer foam, polyvinyl chloride polymerfoam, polystyrene polymer foam, polyimide polymer foam, silicone polymerfoam, polyethylene polymer foam, polyester polymer foam, polypropylenefoam and combinations thereof. While such first layer 94 may have a voidfraction of ninety five (95) percent or greater, in another instancesuch layer 94 may have a void fraction greater than ninety six (96)percent. In further instances, the first layer may have a void fractiongreater than ninety seven (97) percent, or even ninety eight (98)percent.

As demonstrated in FIG. 5, such foam may further include a second layer96, and such second layer 96 may be adhered to the first layer 94. Suchsecond layer 96 may be an adhesive, such as an adhesive polymer. Someadhesive polymers from which the second layer may be made includes, butis certainly not limited to, acrylic polymer, alkyd polymer, styreneacrylic polymer, styrene butadiene polymer, vinyl acetate polymer, vinylacetate homopolymer polymer, vinyl acrylic polymer, vinyl maleatepolymer, vinyl versatate polymer, vinyl alcohol polymer, polyvinylchloride polymer, polyvinylpyrrolidone polymer, casein and combinationsthereof.

Such foam 88 may additionally include a third layer 98 adhered to thesecond layer 96 as depicted in FIGS. 6(a-b). While specificallyreferring to FIG. 6a , it is seen that such third layer 98 may becomprised of a particulate material. Such particulate material fromwhich the third layer 98 may be made includes wax powder, wood flour,polymer powder and combinations thereof. Some wax powders from which thethird layer 98 may be manufactured includes, animal wax powder,vegetable wax powder, mineral wax powder, petroleum wax powder andcombinations thereof. Polymer powders from which the third layer 98 maybe made includes polyurethane polymer powder, polyvinyl chloride polymerpowder, polystyrene polymer powder, polyimide polymer powder,polyethylene polymer powder, polyester polymer powder, polypropylenepolymer powder and combinations thereof. Certainly, other polymerpowders may be utilized to manufacture the third layer 98 of the foam 88for use in the creation of the open-celled metal foam for gas turbineengine fan blades 60.

Such foam 88, comprising the first layer 94, second layer 96 adhered tothe first layer 94 and third layer 98 adhered to the second layer 94 mayhave void fraction less than or equal to ninety five (95) percent. Inanother instance, such foam 88 may have void fraction less than or equalto ninety four (94) percent. In a further instance, such foam 88 mayhave void fraction less than or equal to ninety three (93) percent. Infurther instances, such foam 88 comprising the first layer 94, secondlayer 96 adhered to the first layer 94 and third layer 98 adhered to thesecond layer 94 may have void fraction less than or equal to ninety two(92) percent, ninety one (91) percent or even ninety (90) percent.

Turning now to FIG. 6b , a modification of the foam 88 comprising thefirst layer 94, second layer 96 adhered to the first layer 94 and thirdlayer 98 adhered to the second layer 94, is depicted. As seen there, thethird layer 98 may be characterized as being a substantially morecontinuous, non-particulate, shaped coating. This third layer 98 maytake on such continuous, non-particulate, shaped characteristic upon theexposing the particulate matter of the third layer 98 to heat energythat is at or above the melting temperature of the particulate matter.That is, the particulate matter melts, and subsequently upon cooling,forms a substantially continuous coating of melted particulate matterover the ligaments 90 and nodes 92 of the foam 88. Like the foam 88having a more particulate shaped third layer 98 depicted in FIG. 6a ,this foam 88 with a more continuous third layer 98 may have a voidfraction less than or equal to ninety five (95) percent. In anotherinstance, such foam 88 may have void fraction less than or equal toninety four (94) percent. In a further instance, such foam 88 may havevoid fraction less than or equal to ninety three (93) percent. Infurther instances, such foam 88 comprising the first layer 94, secondlayer 96 adhered to the first layer 94 and third layer 98 adhered to thesecond layer 94 may have void fraction less than or equal to two percent(92), ninety one (91) percent or even ninety (90) percent.

While not depicted in FIGS. 5-6(a-b), such foam 88 may additionallyinclude a fourth layer comprising an adhesive adhered to the thirdlayer. Such adhesive may be an adhesive polymer and may be selected fromthe list of adhesives described above in paragraph [0047].Alternatively, such adhesive may be a different adhesive polymeraltogether. Further, such foam 88 may additionally comprise a fifthlayer adhered to the fourth layer. Such fifth layer may be a particulatematerial and the particulate material may be a powder selected from suchmaterials described in paragraph [0048] of this application. Certainlyother particulate materials are possible. Additional adhesive andparticulate material layers may be added as needed so that the voidfraction of the foam 88 for use in a lost foam casting process is lessthan or equal to ninety five (95) percent.

Turning now to FIG. 7, steps to a method of manufacturing foam 88 foruse in a lost-foam casting process, the foam 88 having a void fractionless than or equal to ninety five (95) percent, are illustrated. At astep 100, polymer foam having an open-cell structure and a void fractiongreater than ninety five (95) percent may be provided. Such polymer foammay be selected, for example, from the group consisting of polyurethanepolymer foam, polyvinyl chloride polymer foam, polystyrene polymer foam,polyimide polymer foam, silicone polymer foam, polyethylene polymerfoam, polyester polymer foam, polypropylene foam and combinationsthereof. At a step 102, the polymer foam may be coated with an adhesive.Such adhesive may be an adhesive polymer, for instance, and may beselected from the group consisting of acrylic polymer, alkyd polymer,styrene acrylic polymer, styrene butadiene polymer, vinyl acetatepolymer, vinyl acetate homopolymer polymer, vinyl acrylic polymer, vinylmaleate polymer, vinyl versatate polymer, vinyl alcohol polymer,polyvinyl chloride polymer, polyvinylpyrrolidone polymer, casein andcombinations thereof. Certainly, other adhesive polymers are possible.At a step 104, a particulate material may be applied to the adhesive,and the particulate material may be chosen from the group consisting ofwax powder, wood flour, polymer powder and combinations thereof.Further, the wax powder may be selected from the group consisting ofanimal wax powder, vegetable wax powder, mineral wax powder, petroleumwax powder and combinations thereof. If a polymer powder is chosen, itmay be selected from the group consisting of polyurethane polymerpowder, polyvinyl chloride polymer powder, polystyrene polymer powder,polyimide polymer powder, polyethylene polymer powder, polyester polymerpowder, polypropylene polymer powder and combinations thereof.Additionally, such particulate material may be applied by passing theadhesive coated polymer foam through a fluidized bed of particulatematerial.

When coating the polymer foam with an adhesive at step 102, such stepmay comprise applying an emulsion to the polymer foam. Such emulsion maycomprise any of the foregoing described adhesive polymers dispersed in asolvent. Further, such step may further include removing the excesssolvent from the polymer foam before applying a particulate material tothe adhesive.

In an addition to the process described above, the polymer foamcomprises ligaments positioned between nodes, and may further compriseheating the foam to a temperature above the melting temperature of theparticulate material, followed by cooling the foam to a temperaturebelow the melting temperature of the particulate material, to form asubstantially continuous coating of particulate material over theligaments.

In an optional additional step, the third layer may be coated with afourth layer, the fourth layer comprising an adhesive. Such adhesive maybe an adhesive polymer selected from the list described above inparagraph [0052], but other adhesive polymers are certainly possible.Then, such fourth layer may be coated with a fifth layer comprisingparticulate material. Such particulate material may be a powder chosenfrom those described above in paragraph [0052], although other materialsare possible. Additionally, such foam 88 may be coated with additionaladhesive and particulate material layers beyond the fourth and fifthlayer until the void fraction of the foam 88 for use in a lost-foamcasting process is less than or equal to ninety five (95) percent.

Referring next to FIG. 8, steps to a method of manufacturing a fan blade60 for a gas turbine engine 20 are depicted. At a step 106, polymer foamhaving an open-cell structure and a void fraction greater than ninetyfive (95) percent may be provided. At a step 108, the polymer foam maybe coated with an adhesive to create adhesive coated foam. At a step110, particulate material may be applied to the adhesive coated foam tomake a modified foam having a void fraction less than or equal to ninetyfive (95) percent. At a step 112, the modified foam having a voidfraction less than or equal to ninety five (95) percent may covered witha refractory material. At a step 114, the refractory material may becured until it hardens and forms an investment. At a step 116, theinvestment may be heated to a temperature above the boiling point of themodified foam having a void fraction less than or equal to ninety five(95) percent to form a negative of the modified foam. At a step 118,molten metal or metal alloy may be added adding to the negative,followed by cooling the negative to a temperature below the meltingtemperature of the metal or metal alloy to form a positive of themodified foam. At a step 120, the refractory material may be removed toform an open-cell metal foam having a void fraction less than or equalto ninety five (95) percent. At a step 122, the open-cells metal foamhaving a void fraction less than or equal to ninety five (95) percentmay be enveloped with an outer shell of a first material, the out shellhaving the shape of an airfoil, to form a fan blade for a gas turbineengine.

In one instance of the foregoing method, the polymer foam ispolyurethane polymer foam, the adhesive is vinyl acetate, theparticulate material is polyethylene polymer powder and the metal ormetal alloy is aluminum. Further, the outer shell of first material maybe made of a metal or metal alloy that is from the group consisting ofaluminum, titanium and nickel, aluminum alloys, steel, nickel alloys andtitanium alloys. Alternatively, the outer shell of first material may bemade of a composite material and this composite material may comprisefiber embedded in resin.

INDUSTRIAL APPLICABILITY

In operation, foam for use in a lost-foam casting process can find usein many industrial applications, such as in the creation of open-cellreticulated metal foams for use in gas turbine engine fan blades. Morespecifically, the foam may find use as a positive in the lost-foamcasting process for open-cell reticulated metal foams. The void fractionof foam utilized in such process is typically ninety seven (97) percent.While not conclusive, data suggests that gas turbine engine fan bladescomprising open-cell reticulated metal foam manufactured from theabove-described foams lack the resilience necessary for use in such fanblades.

Accordingly, the current application describes foam that can be used ina lost-foam casting process to create open-cell reticulated metal foamwith a lesser void fraction. Such foam may include a first layercomprising a polymer foam having a void fraction greater than ninetyfive (95) percent, a second layer comprising an adhesive adhered to thefirst layer and a third layer of particulate material adhered to thethird layer. Such foam, having these three layers, has a void fractionthat is less than or equal to ninety five (95) percent and therefore maybe used in a lost-foam casting process to create an open-cellreticulated metal foam having the necessary resilience to be used in gasturbine engine fan blades. Additionally, methods are described tomanufacture such foam having three layers with the necessary voidfraction. Further, methods are described to create a fan blade for a gasturbine engine utilizing the afore-described foam having three layerswith the necessary void fraction.

The above description is meant to be representative only, and thusmodifications may be made to the embodiments described herein withoutdeparting from the scope of the disclosure. Thus, these modificationsfall within the scope of present disclosure and are intended to fallwithin the appended claims.

What is claimed is:
 1. A foam for use in a lost-foam casting process,the foam having a void fraction less than or equal to ninety fivepercent, comprising: a first layer, the first layer comprising a polymerfoam having an open-cell structure and a void fraction greater thanninety five percent; a second layer, the second layer comprising anadhesive adhered to the first layer; and a third layer, the third layercomprising a particulate material, the third layer adhered to the secondlayer.
 2. The modified foam according to claim 1, wherein the polymerfoam is selected from the group consisting of polyurethane polymer foam,polyvinyl chloride polymer foam, polystyrene polymer foam, polyimidepolymer foam, silicone polymer foam, polyethylene polymer foam,polyester polymer foam, polypropylene foam and combinations thereof. 3.The foam according to claim 1, wherein the adhesive is an adhesivepolymer selected from the group consisting of acrylic polymer, alkydpolymer, styrene acrylic polymer, styrene butadiene polymer, vinylacetate polymer, vinyl acetate homopolymer polymer, vinyl acrylicpolymer, vinyl maleate polymer, vinyl versatate polymer, vinyl alcoholpolymer, polyvinyl chloride polymer, polyvinylpyrrolidone polymer,casein and combinations thereof.
 4. The foam according to claim 1,wherein the particulate material is selected from the group consistingof wax powder, wood flour, polymer powder and combinations thereof. 5.The foam according to claim 4, wherein the wax powder is selected fromthe group consisting of animal wax powder, vegetable wax powder, mineralwax powder, petroleum wax powder and combinations thereof.
 6. The foamaccording to claim 4, wherein the polymer powder is selected from thegroup consisting of polyurethane polymer powder, polyvinyl chloridepolymer powder, polystyrene polymer powder, polyimide polymer powder,polyethylene polymer powder, polyester polymer powder, polypropylenepolymer powder and combinations thereof.
 7. A method of manufacturingfoam for use in a lost-foam casting process, the foam having a voidfraction less than or equal to ninety five percent, comprising:providing a polymer foam having an open-cell structure and a voidfraction greater than ninety five percent; coating the polymer foam withan adhesive; and applying a particulate material to the adhesive.
 8. Themethod of manufacturing the foam according to claim 7, wherein thepolymer foam is selected from the group consisting of polyurethanepolymer foam, polyvinyl chloride polymer foam, polystyrene polymer foam,polyimide polymer foam, silicone polymer foam, polyethylene polymerfoam, polyester polymer foam, polypropylene foam and combinationsthereof.
 9. The method of manufacturing the foam according to claim 7,wherein the adhesive comprises an adhesive polymer, the adhesive polymerselected from the group consisting of acrylic polymer, alkyd polymer,styrene acrylic polymer, styrene butadiene polymer, vinyl acetatepolymer, vinyl acetate homopolymer polymer, vinyl acrylic polymer, vinylmaleate polymer, vinyl versatate polymer, vinyl alcohol polymer,polyvinyl chloride polymer, polyvinylpyrrolidone polymer, casein andcombinations thereof.
 10. The method of manufacturing the foam accordingto claim 7, wherein the particulate material is selected from the groupconsisting of wax powder, wood flour, polymer powder and combinationsthereof.
 11. The method of manufacturing the foam according to claim 10,wherein the wax powder is selected from the group consisting of animalwax powder, vegetable wax powder, mineral wax powder, petroleum waxpowder and combinations thereof.
 12. The method of manufacturing thefoam according to claim 10, wherein the polymer powder is selected fromthe group consisting of polyurethane polymer powder, polyvinyl chloridepolymer powder, polystyrene polymer powder, polyimide polymer powder,polyethylene polymer powder, polyester polymer powder, polypropylenepolymer powder and combinations thereof.
 13. The method of manufacturingthe foam according to claim 7, wherein the coating the polymer foam withan adhesive step comprises applying an emulsion to the polymer foam, theemulsion comprising an adhesive polymer and solvent.
 14. The method ofmanufacturing the foam according to claim 13, further comprisingremoving excess solvent from the polymer foam before applying aparticulate material to the adhesive.
 15. The method of manufacturingthe foam according to claim 7, wherein the polymer foam comprisesligaments positioned between nodes, and further comprising heating thefoam to a temperature above the melting temperature of the particulatematerial, followed by cooling the foam to a temperature below themelting temperature of the particulate material to form a substantiallycontinuous coating of particulate material over the ligaments.
 16. Themethod of manufacturing the foam according to claim 7, wherein theapplying a particulate material to the adhesive includes passing theadhesive coated polymer foam through a fluidized bed of particulatematerial.
 17. A method of manufacturing a fan blade for a gas turbineengine, comprising: providing a polymer foam having an open-cellstructure and a void fraction greater than ninety five percent; coatingthe polymer foam with an adhesive to create an adhesive coated foam;applying a particulate material to the adhesive coated foam to make amodified foam having a void fraction less than or equal to ninety fivepercent; covering the modified foam having a void fraction less than orequal to ninety five percent with a refractory material; curing therefractory material until it hardens to form an investment; heating theinvestment to temperature above the boiling point of the modified foamhaving a void fraction less than or equal to ninety five percent to forma negative of the modified foam; adding molten metal or metal alloy tothe negative, followed by cooling the negative to a temperature belowthe melting temperature of the metal or metal alloy to form a positiveof the modified foam; removing the refractory material to form anopen-cell metal foam having a void fraction less than or equal to ninetyfive percent; and enveloping the open-cell metal foam having a voidfraction less than or equal to ninety five percent with an outer shellof a first material, the shell having the shape of an airfoil, to form afan blade for a gas turbine engine.
 18. The method for manufacturing thefan blade according to claim 17, wherein the polymer foam ispolyurethane polymer foam, the adhesive is vinyl acetate, theparticulate material is polyethylene polymer powder and the metal ormetal alloy is aluminum.
 19. The method for manufacturing the fan bladeaccording to claim 17, wherein the outer shell of a first material ismade of a metal or metal alloy selected from the group consisting ofaluminum, titanium and nickel, aluminum alloys, steel, nickel alloys andtitanium alloys.
 20. The method of manufacturing the fan blade accordingto claim 17, wherein the outer shell of a first material is made of acomposite material, and the composite material is made of fiber embeddedin resin.